One thing I will add:
Many chargers have a 'soft start' to their charging regime, so although you may have set the charge current at 4A you will initially see a lower charger current until the charger kicks in with the current you have set, This is most likely so the charger can validate that the cell voltages are what it expects and there are no cell shorts or under voltage cells.
Also, if you put a battery on charge this is already 90% charged you will see that the voltage goes straight to 8.4V and that the current is already tapering.. this is of course normal.
Lastly, if your charger set set to balance the cells then (at the end of charge) you will see the current rising and falling as the charger attempts to equalize the voltage of each cell, again this is normal. Note that balance charging can take much longer than regular charging.
N
|